Tinnitus is defined as the perception of sound by an individual when no external sound is present, and often takes the form of a hissing, ringing, roaring, chirping or clicking sound which may be intermittent or constant. According to the American Tinnitus Association, tinnitus afflicts more than 50 million Americans, and more than 12 million of those suffer so severely from tinnitus that they seek medical attention and many cannot function normally on a day-to-day basis.
Tinnitus, often referred to as ringing in the ears, is estimated to be present in approximately 50% of the US population over 65 years of age. In general, tinnitus takes many and varied forms, which may be related to its underlying cause. Tinnitus may be caused by, or related to, such diverse factors as trauma, drugs, hearing loss, the normal aging process or other unknown causes.
Previous approaches to treating tinnitus have focused on masking the tinnitus noise experienced by patients. While previous masking techniques have been unable to alleviate the problems of tinnitus patients, significant research has been done. In reporting on studies at the Oregon Tinnitus Clinic, Jack Vernon, director of the Oregon Hearing Research Center, stated that, in patient tinnitus studies, phase and tone relationships are of obvious and critical importance in tone masking of tinnitus. Vernon goes on to observe that one cannot repress the idea of canceling tinnitus by a proper phase adjustment of the external tone used in masking.
In commenting on Wegel's earlier tinnitus treatment findings that a slight mistuning of a masking external tone produced a beat-like sensation with the tinnitus sound, Vernon reported that, in a 100 patient study, he was able to detect a slight beat-like sensation in only four instances. Vernon therefore concluded that the beat-like sensation found by Wegel was most probably due to octave confusion resulting from Wegel not using a single pure tone, but rather a narrow band of noise. In conclusion, Vernon observed that phase manipulation justifies further patient studies as a masking parameter for tonal tinnitus treatments. Vernon's report on possible phase manipulation for treating tinnitus patients remained unchanged from its original publication in 1991 and as included in the 1997 edition of Shulman's treatise entitled “Tinnitus Diagnosis and Treatment.”
In his above-referenced U.S. Application, Dr. Choy reports on favorable patient data from blind clinical studies utilizing a 180-degree phase shift of an externally generated tinnitus tone. More than 79% of patients studied reported either elimination of, or substantial reduction in the level of, tinnitus noise.
Neither current medical procedures nor electronic or sonic instrumentation permit or facilitate an objective determination of either the frequency or amplitude of the tinnitus noise a patient experiences. It is also not possible to subjectively determine an instantaneous phase of a point on a patient's virtual mono-frequency tinnitus tone.
This current state of tinnitus treatment has been bothersome for the tinnitus patient because the current state of medical knowledge and acoustic/electronics instrumentation does not yet permit one to objectively determine at what point on a patient's virtual endogenous tinnitus sound wave tinnitus tone (sine wave) an exogenous phase-shifted sine wave would be inserted in an attempt to cancel the patient's virtual tinnitus noise.